1. Field of the Invention
The present invention relates to a DSL communication apparatus and a download method of a DSL communication program that are suitable for data transmission apparatus using a multi-carrier method, the method performing data transmission using a plurality of carriers having different frequencies.
2. Description of Related Art
The ADSL (Asymmetric Digital Subscriber Line) is a service that employs an existing telephone line so that both a high speed Internet connection service and ordinary telephone service can use the same line, which has rapidly become available in the recent years. For providing such ADSL services, ITU-T recommendations have been issued regarding ADSL modems. G.lite and G.dmt recommendations established in 1999 at ITU-T SG15 are ADSL standard recommendations, which further extend to ANNEX.A, ANNEX.B, ANNEX.C, and etc., for initialization establishing methods according to the communication environment of individual country (or region).
An ADSL communication apparatus has a resident memory (hereafter referred to as execution memory) in which a DSP within a transceiver executes a necessary program during ADSL communication.
During the ADSL communication, a handshake sequence is executed according to a protocol such as G.hs, in order to exchange capability information and manufacturer codes between ADSL communication apparatuses. For example, G.dmt is a protocol for ADSL communication that can transmit data at 1.5 Mbps, while G.lite is a protocol for ADSL communication that can transmit data at 8 Mbps. Both protocols have specifications such as ANNEX.A, ANNEX.B, and ANNEX.C, in order to accommodate communication environments in various counties and regions.
Capability information exchanged during the handshake sequence is checked to verify which protocol is supported by an opposing communication apparatus. ADSL communication becomes available when both communication apparatuses support the same protocol to be used.
According to the protocol determined during the handshake sequence (G.dmt or G.lite), an initialization sequence is executed to exchange various parameters to be used during the data transmission. When the initialization sequence is completed, data transmission (SHOWTIME) is initiated.
However, memory has not been used effectively when programs, in accordance with each protocol for handshake and initialization sequences, occupy the execution memory within the transceiver. In addition, when programs with large capacities occupy the execution memory, it becomes a burden for DSP to process, which slows down the processing speed. Especially, since ADSL communication performs a type of communication that is always connected, it is no necessary to repeat the sequences once the handshake and initialization sequences are performed, unless there is a communication error. Therefore, it is not necessary store the programs corresponding to different protocols for the handshake and initialization sequences after the connection is established. Further, as described above, the ADSL communication method employs G.dmt or G.lite method, each having specifications such as ANNEX.A, ANNEX.B, and ANNEX.C., which were difficult to be stored in the execution memory within the transceiver, because of the memory capacity limitation.